Applies data attributes to selector tooltips, fixes #6832

This commit fixes #6832, by applying options provided in data attributes before showing and hiding tooltips with a selector. 

In the doc there is something like this:

```html
<div class="bs-docs-example tooltip-demo">
  <ul class="bs-docs-tooltip-examples">
    <li><a href="#" data-toggle="tooltip" data-placement="top" title="" data-original-title="Tooltip on top">Tooltip on top</a></li>
    <li><a href="#" data-toggle="tooltip" data-placement="right" title="" data-original-title="Tooltip on right">Tooltip on right</a></li>
    <li><a href="#" data-toggle="tooltip" data-placement="bottom" title="" data-original-title="Tooltip on bottom">Tooltip on bottom</a></li>
    <li><a href="#" data-toggle="tooltip" data-placement="left" title="" data-original-title="Tooltip on left">Tooltip on left</a></li>
  </ul>
</div>
```

The tooltip plugin are then attached like so:

```javascript
$('.tooltip-demo').tooltip({
  selector: "a[data-toggle=tooltip]"
})
```

Without applying the data attribute options, only the options in given to to the `tooltip( .. )` are used and all the delegated tooltips use the default placement (as well as other defaults).

I don't know if this is something you want to support, alternatively docs could be updated to attach the tooltips differently.